Well, this really isn't a microphone question, so it should be posted in the "Computer Recording and Soundcard" forum. Still, there are plenty of soundcards under $150. How many inputs do you need at once? At that price, I would be looking at the M-Audio Delta 44, which has 4 analog inputs.
BTW, a soundcard allows you to record and listen to music on your computer. It contains an Analog-to-Digital and Digital-to-Analog converter chip(s) for this purpose. If you can listen to music on your computer, you already have a soundcard. However, most soundcards that come with computers are not designed for recording music and will generally suck for that application.
